The present invention relates to a system for detecting or identifying individual railroad cars as they move in a train along a track. More particularly, the present invention relates to a system for detecting railroad cars which have no label, stripe, transponder or other means of identification.
The term "railroad car", as used herein, is defined as any type or rolling railroad stock such as, but not limited to, a locomotive, box car, tank car, ore car, flat car, caboose and passenger car.
Various techniques have been employed to detect and count moving railroad cars. One such technique is to simply count the number of axles in a train and to assume that each car in the train has a certain number of axles (four, for example). Such a system is useful in situations where only one type of car, such as an ore car, is being counted but it cannot be employed when the types of cars may vary.
Another car-detecting technique, which distinguishes between two types of railroad cars, is disclosed in the German patent publication (DAS) No. 1,015,037. In this system, the distance between the axles of two-axle cars provides a criterion for differentiating between cars. Wheel sensors, arranged along the track, are coupled to an electronic switching network which determines whether the car is of one type or another.
Other car-detecting techniques are known which require some form of identification on each railroad car. For example, the car may be provided with a painted "stripe" at a particular level which is optically scanned as the car passes by. Each car may also be provided with a transponder that transmits a unique identification code in response to an interrogation from a stationary transmitter arranged adjacent to the track.
None of the systems described above are capable of accurately detecting the presence of railroad cars in a train (1) without prior knowledge of the type of cars in the train, and/or (2) without some means of identification arranged on each car.